OLYMPIA, Washington (Reuters) - The former head of a Democratic Party fundraising committee in Washington state has been charged with embezzling up to $300,000 in campaign contributions to feed a gambling habit, prosecutors said on Wednesday.

Michael King, 32, concealed the theft from the Senate Democratic Campaign Committee in part by reporting it as a series of phony reimbursements for political polling, according to charges filed by the King County prosecutor's office.

"It's a very serious theft and he's facing a long prison sentence," King County Prosecutor's spokesman Dan Donohoe said, adding that King could face up to 29 months in prison for thefts that occurred between March 2011 and January 2013.

An attorney for King, Lyle Tenpenny, could not immediately be reached for comment.

The case raises questions about whether state Senate Democrats were fighting at a self-inflicted disadvantage in last year's election campaign, after which they held a 26 to 23 majority but lost control of the chamber when two conservative Democrats opted to caucus with Republicans to form a majority coalition.

State Senate Democrats netted a loss of one seat in 2012, a year in which the party handily won the governor's race and President Barack Obama won the state by 15 points over Republican challenger Mitt Romney.

Among the races the party lost in 2012 was one where conservative Republican state Senator Don Benton retained his seat by a 74-vote margin.

According to the charging documents, King spent the money on alcohol and gambling, with a review of his bank records showing dozens of withdrawals to at least three area casinos.

In a Wednesday conference call with reporters, the three state senators who co-chaired the now-defunct committee said that its treasurer, Jason Bennett, gave King check-writing authority without their knowledge or consent.

"It's not like legislators are in the campaign office every single day supervising," said Senate minority leader co-chair Ed Murray, who is also the front-running challenger in the Seattle mayor's race.

Bennett said he did not have supervisory authority over King.

King has been charged with four counts of first-degree theft and four counts of second-degree theft. He faces a maximum sentence of 22 to 29 months in prison and up to $20,000 in fines, Donohoe said.

King has made a full confession to police, the charging documents said. He is scheduled to be arraigned at the King County Courthouse in Seattle on October 7. He is not currently in custody, Donohoe said, as he is not seen as a flight risk.